1.For the source code just check out from SVN:
svn checkout http://jforum2.googlecode.com/svn/trunk/ jforum2-read-only
2.user_list_karma.htm is disabled in karma_search.inc.htm since previous version. As I know, karma value is changed only through post rating. You cannot assign someone with a specific karma value. So there is no admin control panel for this.